linux-kernel - Re: [PATCH v2 08/17] KVM: TDX: Complete interrupts after TD exit

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Message-ID: <Z62rPgmS2RB/LaC7@intel.com>
Date: Thu, 13 Feb 2025 16:20:14 +0800
From: Chao Gao <chao.gao@...el.com>
To: Binbin Wu <binbin.wu@...ux.intel.com>
CC: <pbonzini@...hat.com>, <seanjc@...gle.com>, <kvm@...r.kernel.org>,
	<rick.p.edgecombe@...el.com>, <kai.huang@...el.com>,
	<adrian.hunter@...el.com>, <reinette.chatre@...el.com>,
	<xiaoyao.li@...el.com>, <tony.lindgren@...el.com>,
	<isaku.yamahata@...el.com>, <yan.y.zhao@...el.com>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 08/17] KVM: TDX: Complete interrupts after TD exit

>+static void tdx_complete_interrupts(struct kvm_vcpu *vcpu)
>+{
>+	/* Avoid costly SEAMCALL if no NMI was injected. */
>+	if (vcpu->arch.nmi_injected) {
>+		/*
>+		 * No need to request KVM_REQ_EVENT because PEND_NMI is still
>+		 * set if NMI re-injection needed.  No other event types need
>+		 * to be handled because TDX doesn't support injection of
>+		 * exception, SMI or interrupt (via event injection).
>+		 */
>+		vcpu->arch.nmi_injected = td_management_read8(to_tdx(vcpu),
>+							      TD_VCPU_PEND_NMI);
>+	}

Why does KVM care whether/when an NMI is injected by the TDX module?

I think we can simply set nmi_injected to false unconditionally here, or even in
tdx_inject_nmi(). From KVM's perspective, NMI injection is complete right after
writing to PEND_NMI. It is the TDX module that should inject the NMI at the
right time and do the re-injection.


>+}
>+